Here’s what you need to know now about the powerful storm that forecasters say is gaining strength:

• Hurricane Matthew remains a Category 4 storm with winds of 140 mph, according to the latest National Hurricane Center advisory. As of 2 p.m. ET, Matthew was located about 125 miles east-southeast of West Palm Beach, Florida, and is expected to make a northwest turn toward the peninsula sometime Thursday night or early Friday.

• Daytona Beach, Florida, Mayor Derrick Henry told CNN he fears residents might be emboldened by the fact that his city hasn’t seen a direct hit from a hurricane in four decades. “We’re not immune. … Get out. That is our message and that is our hope. Worry about your possessions later. Take care of your life now. You only have one life,” he said. St. Augustine Mayor Nancy Shaver issued a similar warning.

• Authorities urged more than 2 million people to leave their homes in coastal Florida, Georgia and South Carolina as the storm neared — the largest mandatory evacuations in the United States since Hurricane Sandy hit the East Coast in 2012.

“Hurricane Matthew is a storm not to be messed with. If you decide to ride it out, do not expect us to be there to help you. We will not risk the lives of our emergency responders to save those who refused to heed this evacuation call,” he said in a statement.

CNN affiliate WSB reported 20-mile long traffic backups on I-75 northbound, south of metro Atlanta, as people from coastal areas sought to flee the storm.